AAO-based light guiding structure and fabrication thereof

ABSTRACT

A light guiding structure is provided. The structure includes an anodized aluminum oxide (AAO) layer and a fluoropolymer layer located immediately adjacent to a surface of the AAO layer. Light propagates through the AAO layer in a direction substantially parallel to the fluoropolymer layer. An optoelectronic device can be coupled to a surface of the AAO layer, and emit/sense light propagating through the AAO layer. Solutions for fabricating the light guiding structure are also described.

REFERENCE TO RELATED APPLICATIONS

The current application claims the benefit of U.S. ProvisionalApplication No. 62/050,126 and U.S. Provisional Application No.62/050,127, both of which were filed on 13 Sep. 2014, and both of whichare hereby incorporated by reference.

TECHNICAL FIELD

The disclosure relates generally to light guiding structures, and moreparticularly, to fabrication of a light guiding structure including ananodized aluminum oxide (AAO) layer.

BACKGROUND ART

Compact diodes emitting in the ultraviolet (UV) domain recently havematured to be used in industrial, engineering, scientific, and medicalapplications. These light sources are used for disinfection, polymercuring, and skin illness treatment. In phototherapy, detrimental sideeffects can be minimized by carrying light through fiber optics so thata small output beam can be targeted at selected areas of the infectedskin. Other applications of UV radiation include coherent anti-StokesRaman scattering and fluorescence imaging.

A commonly utilized transparent material for guiding UV light includessolid-core fibers fabricated based on fused silica. In addition, the useof hollow-core photonic crystal fiber (HC-PCF) allowing weak interactionbetween the glass material and the light may assist in overcoming somedrawbacks presented in solid-core fused silica fibers. For example, inthe infrared (IR) region of the electromagnetic spectrum, HC-PCFs havebeen shown to guide light with loss thirty times lower than that of itsglassy constituent. To this extent, an HC-PCF-based design for efficientpropagation of UV light at wavelengths of 355 nm has been suggested.

A group considered using photonic crystal fibers (PCFs) for single-modedelivery of UV wavelengths in the range ˜200-300 nm. Typical PCFs have auniform patterned microstructure of holes (defects) running axiallyalong the fiber channel with a missing hole in the center providing acore region. In an equivalent index-of-refraction picture, themicrostructure imposes a strong wavelength dependence on theindex-of-refraction of the cladding, and for high light frequencies(short wavelengths) the cladding index approaches the core index. Withappropriate fiber design, the fiber core can support a single guidedmode over all optical frequencies, a characteristic referred to asendless single-mode operation.

Similarly, a group studied single-mode optical fiber use in high-power,low-loss UV transmission. The group reported large-mode-area solid-corephotonic crystal fibers made from fused silica that resist ultraviolet(UV) solarization even at relatively high optical powers. Using aprocess of hydrogen loading and UV irradiation of the fibers, the groupdemonstrated stable single-mode transmission over hundreds of hours forfiber output powers of 10 mW at 280 nm and 125 mW at 313 nm (limitedonly by the available laser power). Fiber attenuation ranges from 0.9dB/m to 0.13 dB/m at these wavelengths, and was unaffected by bendingfor radii above 50 mm.

Liquid core waveguide or light guiding structures can be beneficial forguiding ultraviolet (UV) radiation, e.g., due to the low UV absorbanceproperties of some liquids, such as purified water. The generalavailability of water allows for the fabrication of relativelyinexpensive light guides for UV radiation that can be readily adoptedfor use in industry. Combined with a light guide enclosure formed of afluoropolymer having low UV absorbance and other beneficial properties(e.g., chemical inertness, low biological contamination), the benefitsof thin light guiding UV layers can be easily appreciated.

These light guiding structures, or so-called liquid core waveguides orflow cells, have been developed for optical spectroscopy applications inthe ultraviolet, visible, and infrared regions of the light spectra.Such flow cells are particularly suitable when combined with opticalfibers for light transfer, enabling the design of a flexible sensorsystem. A number of flow cells having a long optical path length havebeen designed for absorbance, fluorescence, and Raman spectroscopy.Similar to optical fibers, light is confined in such flow cells withinthe (liquid) core by total internal reflection (TIR) at the liquidcore/wall interface or the liquid core/cladding (coating) interface. Theonly requirement is that the liquid core refractive index be higher thanthat of the refractive index of the ambient. For liquid core comprisingpurified water, and for ambient being air, this requirement is easilysatisfied.

One approach to employ liquid-based light guiding structures describes areactor configuration for UV treatment of water utilizing TIR and a flowtube. The inlet and core of the cylindrical tank reactor unit is atransparent flow tube that is surrounded by a sealed, concentric volumeof material having a lower refractive index than the fluid flowing inthe flow tube, which enables TIR of UV light when it is directed axiallyinto the flow tube. Another approach discloses a method and reactor forin-line treatment of fluids and gases by light radiation comprising atube or a vessel made of transparent material, preferably quartz glass,and surrounded by air, and having a fluid inlet, a fluid outlet, and atleast one opening or window adapted for the transmission of light froman external light source into the tube. Air outside the tube or vesselhas a lower refractive index compared to the treated fluid, whichenables TIR. Still other approaches discuss various aspects of a liquidcore light guide. One such approach discusses a liquid core waveguidephoton energy material processing system.

SUMMARY OF THE INVENTION

Aspects of the invention provide a light guiding structure. Thestructure includes an anodized aluminum oxide (AAO) layer and afluoropolymer layer located immediately adjacent to a surface of the AAOlayer. Light propagates through the AAO layer in a directionsubstantially parallel to the fluoropolymer layer. An optoelectronicdevice can be coupled to a surface of the AAO layer, and emit/senselight propagating through the AAO layer. Solutions for fabricating thelight guiding structure are also described.

A first aspect of the invention provides a structure including: ananodized aluminum oxide (AAO) layer; and an optoelectronic devicecoupled to a side of the AAO layer, wherein the optoelectronic device ispositioned at a target angle with respect to light propagating throughthe AAO layer.

A second aspect of the invention provides a light guiding structurecomprising: an anodized aluminum oxide (AAO) layer; and a fluoropolymerlayer located immediately adjacent to a surface of the AAO layer,wherein light propagates through the AAO layer in a directionsubstantially parallel to the fluoropolymer layer.

A third aspect of the invention provides a method comprising:fabricating a structure including: an anodized aluminum oxide (AAO)layer; and a fluoropolymer layer located immediately adjacent to asurface of the AAO layer, wherein light propagates through the AAO layerin a direction substantially parallel to the fluoropolymer layer.

The illustrative aspects of the invention are designed to solve one ormore of the problems herein described and/or one or more other problemsnot discussed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the disclosure will be more readilyunderstood from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings that depict various aspects of the invention.

FIGS. 1A and 1B show illustrative light guiding structures according toembodiments.

FIG. 2 shows an illustrative light guiding structure according toanother embodiment.

FIGS. 3A and 3B show illustrative light guiding structures according toother embodiments.

FIGS. 4A-4C illustrate fabrication of an illustrative light guidingstructure according to an embodiment.

FIG. 5 shows an illustrative light guiding structure according toanother embodiment.

FIGS. 6A-6C show an illustrative process for patterning a fluoropolymerlayer according to an embodiment.

FIGS. 7A and 7B show illustrative utilizations of surface-patternedfluoropolymer layers in a light guiding structure according toembodiments.

FIGS. 8A-8F show an illustrative process for forming a light guidingstructure according to an embodiment.

It is noted that the drawings may not be to scale. The drawings areintended to depict only typical aspects of the invention, and thereforeshould not be considered as limiting the scope of the invention. In thedrawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION OF THE INVENTION

As indicated above, aspects of the invention provide a light guidingstructure. The structure includes an anodized aluminum oxide (AAO) layerand a fluoropolymer layer located immediately adjacent to a surface ofthe AAO layer. Light propagates through the AAO layer in a directionsubstantially parallel to the fluoropolymer layer. An optoelectronicdevice can be coupled to a surface of the AAO layer, and emit/senselight propagating through the AAO layer. Solutions for fabricating thelight guiding structure are also described. Embodiments of the lightguiding structure can have thicknesses (as measured in a directiontransverse to the propagation of light there through) of severalmicrometers.

Aspects of the invention can provide a method of fabricating a lightguiding structure that can be thin (e.g., can be on the order of fewmicrons, or even on the order of hundreds of nanometers) and can beeasily utilized in small thin devices. An embodiment further provides alight guiding structure having a thickness on the order of few microns,or even on the order of hundreds of nanometers. Another embodimentprovides a device, which includes a light guiding structure describedherein.

As used herein, unless otherwise noted, the term “set” means one or more(i.e., at least one) and the phrase “any solution” means any now knownor later developed solution. As also used herein, a layer is atransparent layer when the layer allows at least ten percent ofradiation having a target wavelength, which is radiated at a normalincidence to an interface of the layer, to pass there through. A layeris highly transparent when the layer allows at least thirty percent ofthe radiation to pass there through, and a layer is substantiallytransparent when the layer allows at least eighty percent of theradiation to pass there through. Furthermore, as used herein, a layer isa reflective layer when the layer reflects at least ten percent ofradiation having a target wavelength, which is radiated at a normalincidence to an interface of the layer and is highly reflective when thelayer reflects at least eighty percent of the radiation. It isunderstood that a layer can be both transparent and reflective. In anembodiment, the target wavelength of the radiation corresponds to awavelength of radiation emitted or sensed (e.g., peak wavelength +/−five nanometers) by an active region of an optoelectronic device duringoperation of the device. For a given layer, the wavelength can bemeasured in a material of consideration and can depend on a refractiveindex of the material. It is understood that, unless otherwisespecified, each value is approximate and each range of values includedherein is inclusive of the end values defining the range.

Turning to the drawings, FIGS. 1A and 1B show illustrative light guidingstructures 10A, 10B according to embodiments. As illustrated, each lightguiding structure 10A, 10B includes a multi-layer structure 12 includinga substrate 14, an aluminum layer 16, and an anodized aluminum oxide(AAO) layer 18. The substrate 14 can comprise any suitable substrate forforming an AAO layer 18 thereon. The substrate 14 can be formed of anysolid material capable of supporting an aluminum layer 16 thereon. Forformation of the AAO layer 18, the aluminum layer can be accessible toan electrode. The multi-layer structure 12 can be fabricated using anysolution. For example, fabrication can include depositing a layersubstantially consisting of aluminum (e.g., having a thickness of thelayers 16, 18) and performing an anodizing treatment to the aluminumlayer (e.g., by causing the aluminum layer to oxidize), thereby formingthe AAO layer 18 including a plurality of pores 19 and a remainingaluminum layer 16 through which the pores 19 do not extend.

Formation of the AAO layer 18 includes forming the plurality of pores 19within the AAO layer 18 during an anodizing treatment. In an embodiment,at least some of the pores 19 extend through the AAO layer 18 andpartially into the aluminum layer 16. In a more particular embodiment,substantially all of the pores 19 extend through the AAO layer 18. Theattributes of the pores 19, including a characteristic size of the pores19 (e.g., average diameter), a maximum depth of the pores 19, a densityof the pores 19, and/or the like, can vary depending on a particularanodization procedure utilized. For example, an electrolyte (e.g.,oxalic acid, phosphoric acid, sulfuric acid, malonic acid, and/or thelike) and a corresponding concentration of the electrolyte can beselected based on a planned pore size. Subsequently, the AAO layer 18can be formed by placing an aluminum film into the selected electrolytehaving the corresponding concentration, and applying a voltage potentialin a range of approximately 35 Volts to approximately 45 Volts for atime period in the range of several hours.

The anodization procedure can be followed by etching the anodizedaluminum oxide. For example, such etching can comprise chemical etchingincluding: etching in chromic acid and phosphoric acid while atemperature is in the range of 65-80° C. The phosphoric acid can be inthe range of 6 wt to 7 wt % and the chromic acid can be in the range of2 wt % to 3 wt %.

Furthermore, a second anodization can be performed by repeating aprocess substantially similar to or identical to the first anodization.In this case, hexagonally arranged nanoporous structures can be formedwith one end blocked by the underlying substrate 14 and/or a remainingportion of the aluminum layer 16. A process time for the secondanodization can be selected based on a target membrane thickness, andcan range, for example, from one hour to forty-eight hours depending onthe desired membrane thickness (e.g., a desired depth of the AAO pores19).

Anodization can be preceded by electropolishing of aluminum depositedover the substrate 14, or electropolishing an aluminum substrate. Theelectropolishing may involve placing the aluminum in a mixture ofperchloric acid and ethanol, where the ratio of respective chemicals isin the range of 1:3 to 1:5 by volume and a purity of the ethanol is inthe range of 99%-99.9% and a purity of the perchloric acid is in therange of 69-72%. Subsequently, a voltage potential in a range ofapproximately ten volts to approximately twenty volts can be applied ata temperature less than 10° Celsius for 3 to 10 minutes depending on atarget surface roughness.

The structure 12, and particularly the AAO layer 18, can be used as alight guiding structure. To this extent, an optoelectronic device 20A,20B can be coupled to the structure 12 using any solution. Duringoperation, the AAO layer 18 can act as a light guiding layer for lightpropagating to/from the optoelectronic device 20A, 20B. Illustrativeoptoelectronic devices 20A, 20B include a conventional or superluminescent light emitting diode, a light emitting laser, a laser diode,a light sensor, a photodetector, a photodiode, an avalanche diode,and/or the like. In an embodiment, the optoelectronic device 20A, 20B isconfigured to operate as an ultraviolet light emitting device. Theoptoelectronic device 20A, 20B can be coupled to the structure 12 usinga coupler 22A, 22B transparent to light of a target wavelength (e.g.,the primary wavelength emitted/sensed by the optoelectronic device 20A,20B).

The coupler 22A, 22B can be configured to position the optoelectronicdevice 20A, 20B at a target angle with respect to light propagatingthrough the structure 12. In an embodiment, the light propagates throughthe AAO layer 18 in a direction substantially parallel to a top surfaceof the AAO layer 18 and the aluminum layer 16. It is understood that the“a direction substantially parallel” means that the average light raysare moving in the direction. It is understood that individual light rayswill be traveling in various directions. Regardless, the angle can beselected to provide maximum light guiding of light emitted by theoptoelectronic device 20A, 20B. To this extent, the angle can be suchthat a majority of light emitted by the optoelectronic device 20A, 20Benters the structure 12 at an angle optimal for wave guiding, e.g., atan angle larger than the total internal reflection angle for thestructure 12. Similarly, the angle can be selected such that a majorityof light propagating through the structure 12 is directed onto a sensingsurface of the optoelectronic device 20A, 20B for sensing the light. Asillustrated in FIG. 1A, the optoelectronic device 20A can be coupled toa side surface (e.g., top) of the AAO layer 18. Alternatively, asillustrated in FIG. 1B, the optoelectronic device 20B can be coupled toan edge surface of the AAO layer 18. While only a single optoelectronicdevice 20A, 20B is shown in each of the drawings, it is understood thatany number of optoelectronic devices 20A, 20B can be coupled to thestructure 12 in any of various possible combinations of locations.

In an embodiment, the coupler 22A, 22B is formed of afluoropolymer-based material. Illustrative fluoropolymers forming thecoupler 22A, 22B include: fluorinated ethylene-propylene (EFEP),fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA),tetrafluoroethylene hexafluoropropylene vinylidene fluoride (THV),polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF),ethylene-tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene(ECTFE), polychlorotrifluoroethene (PCTFE), a copolymer oftetrafluoroethylene and perfluoromethylvinylether (MFA), low densitypolyethylene (LDPE), perfluoroether (PFA), and/or the like. However, itis understood that the coupler 22A, 22B can be formed from any type ofultraviolet transparent material including, for example, polylactide(PLA), THE, fused silica, sapphire, any combination of two or moreultraviolet transparent materials, and/or the like.

In an embodiment, the coupler 22A, 22B can provide additionalfunctionality. For example, FIG. 2 shows an illustrative light guidingstructure 100 according to another embodiment. In this case, anoptoelectronic device 20C is embedded in an encapsulating layer 24formed on the AAO layer 18 of the structure 12. The encapsulating layer24 can be formed of any material transparent to light of a targetwavelength, such as ultraviolet light. To this extent, the encapsulatinglayer 24 can be formed of a fluoropolymer-based material as describedherein. In an embodiment, the AAO layer 18 can include a surface, suchas the surface on which the encapsulating layer 24 is located, having aregion configured to scatter light propagating there through. In thiscase, formation of the AAO layer can further include depositing aluminumdroplets (islands) over the aluminum layer prior to anodizing thealuminum layer to form the AAO. The subsequent anodization process cananodize both a portion of the original aluminum layer as well as thealuminum droplets located thereon.

It is understood that a light guiding structure described herein caninclude any of various combinations of layers formed of AAO, afluoropolymer, a material having a low refractive index (e.g., ambientair), a reflective material, and/or the like. As used herein, a lowrefractive index material means a material having a refractive index atmost ninety percent of the refractive index of the material formingadjacent layer(s) in a structure.

To this extent, FIGS. 3A and 3B show illustrative light guidingstructures 10D, 10E, respectively, according to other embodiments. Ineach light guiding structure 10D, 100, similar to the structure 10Bshown in FIG. 1B, an optoelectronic device 20B is mounted to an edgeside of the structure 10D, 10E using a coupler 22B. In FIG. 3A, thelight guiding structure 10D further includes a transparent film 26(e.g., a fluoropolymer film) formed on the AAO layer 18 and a reflectivefilm 28 formed on the transparent film 26. The reflective film 28 can beformed of any reflective material, such as polytetrafluoroethylene(e.g., Teflon), aluminum, polished aluminum, and/or the like, and can beuniform or non-uniform. In an embodiment, the reflective film 28 has areflectivity tailored to a set of desired characteristics of thestructure 10D.

In an embodiment, the reflective film 28 has a variable spatialreflectivity. For example, a reflectivity of the reflective film 28 candecrease with distance away from the optoelectronic device 20B. It isunderstood that the reflective film 28 can be partially transparent andpartially reflective, while maintaining constant absorption. Theabsorption characteristics of the reflective film 28 can be sufficientlysmall to allow significant light guiding and transmission. For example,as reflectivity of the reflective film 28 decreases, the transmission ofthe reflective film 28 can increase. Such changes in reflectivity of thereflective film 28 can promote uniform emission of light from anexternal surface of the reflective film 28. For example, the reflectivefilm 28 can comprise a thin aluminum layer having openings wherein asize and/or density of the openings changes with distance from theoptoelectronic device 20B to yield a target overall reflective andtransparent properties of the reflective film 28. Alternatively, thereflective film 28 can comprise an alloy of reflective and transparentmaterials with a varying alloy composition.

The reflectivity of the reflective film 28 can be tailored for aparticular application of the light guiding structure 10D. For example,the reflectivity of the reflective film 28 can have a linear profilefrom highly reflective (near the optoelectronic device 20B) to a highlytransparent film throughout a length of the light guiding structure 10D.The reflectivity can range from a highly reflective film to completetransparency. Moreover, a type of reflectivity of the film can beattenuated as well. For example, the reflective film 28 can bespecularly reflective in some domains while being diffusively reflectivein other domains. Similarly, a transparency of the reflective film 28can be specular or diffusive and can, in general, vary throughout thereflective film 28 depending on the application needs.

In FIG. 3B, the structure 10E further includes a gap layer 30 locatedbetween the transparent film 26 and the reflective film 28. In anembodiment, the gap layer 30 is formed of a transparent fluid. In a moreparticular embodiment, the fluid is a gas, such as ambient air. The gaplayer 30 can be formed using any solution. In an embodiment, the gaplayer 30 is formed using a solution described in U.S. ProvisionalApplication No. 62/050,126. In a more particular embodiment, the gaplayer 30 includes a support structure, such as a plurality of pillars,which can be formed of a fluoropolymer material. Inclusion of the gapfilm 30 can provide improved total internal reflection from theinterface. The reflective film 28 can provide protection againstcontamination. In an embodiment, a structure includes a secondtransparent film as a protective layer instead of the reflective film28.

An embodiment of a structure described herein can include two or moreAAO layers 18. For example, FIGS. 4A-4C illustrate fabrication of anillustrative light guiding structure 10F according to an embodiment.Initially, an interim structure similar to that shown and described inconjunction with FIG. 1B can be obtained (e.g., fabricated).Additionally, a transparent layer 26 can be applied on the AAO layer 18as described herein. A second AAO layer 32 can be applied to thetransparent layer 26 using any solution. For example, the second AAOlayer 32 can be formed on an aluminum layer 34 using a process describedherein. Subsequently, the structure can be turned to apply the AAO layer32 to the transparent layer 26. In an embodiment, the transparent layer26 is formed of a fluoropolymer-based material, which can be heated toenable the AAO layer 32 to fuse with the transparent layer 26.

In an embodiment, one or more conditions used to fabricate the AAOlayers 18, 32 can differ. To this extent, the variation can result inpores 33 of the AAO layer 32 having a different size, spacing, and/orthe like, from the pores 19 (FIG. 1B) of the AAO layer 18. The differingpores 19, 33 can result in a different averaged index of refraction forthe AAO layers 18, 32. Similar to the AAO layer 18, the AAO layer 32 caninclude an adjacent aluminum layer 34 through which the pores 33 do notextend. In an embodiment, the aluminum layer 34 can be removed using anysolution.

For example, the aluminum layer 34 can be chemically removed using avoltage pulse solution. In this case, the aluminum layer 34 can beplaced in a mixture of perchloric acid and ethanol, where the ratio ofrespective chemicals is in the range of 1:3 to 1:5. Subsequently, avoltage pulse from 45 to 50 V can be applied for 3 to 5 seconds, causingthe aluminum layer 34 to detach from the AAO layer 32. FIG. 4B shows theresulting structure 10F, and FIG. 4C shows a perspective view of the AAOlayer 32. By removing the aluminum layer 34, AAO layers 18, 32 ofdifferent types can be stacked in order to create a light guidingstructure 10F having any desired number of AAO layers.

It is understood that a solution for fabricating a structure 10Fincluding multiple AAO layers 18, 32 can be implemented using any ofvarious alternative processes. For example, in an embodiment, prior toapplying the AAO layer 32 to the structure 10F, a handler layer can beapplied to the upper portion of the AAO layer 32 after it is grown onthe aluminum layer 34. The handler layer can be relatively thick andformed of a material capable of being attached and detached to the AAOlayer 32, e.g., a fluoropolymer such as EFEP. The handler layer can beused to manipulate the AAO layer 32 during a process of detaching thealuminum layer 34 from the AAO layer 32. The AAO layer 32 can beattached to another AAO layer, e.g., by fusing the two layers with afluoropolymer layer similar to the AAO layers 18, 32 and fluoropolymerlayer 26. The handler layer can be removed using any solution, such as,chemical etching, dissolving, and/or the like.

Several AAO layers having any combination of attributes can be stackedover each other using this approach. For example, FIG. 5 shows anillustrative light guiding structure 10H according to anotherembodiment. In this case, the structure 10H includes three AAO layers18, 32, 38, and three fluoropolymer layers 26, 36, 40. The pore size andspacing of each AAO layer 18, 32, 38 affects the optical properties ofthe layer (such as transmission, index of refraction, and lightscattering). As a result, selection of the properties of the AAO layers18, 32, 38 can be configured to provide an optimal performance of thelight guiding structure 10H for a given target application. In anembodiment, the AAO layers 18, 32, 38 have pore sizes, spacing,thicknesses, and/or the like, which are selected to produce a targetgraded index of refraction for the structure 10G. In a more particularembodiment, the AAO layer 18 can have pores 19 (FIG. 1B) havingdiameters in a range of 150 nm to 200 nm and separated by distances(e.g., as measured edge to edge) on the order of 400 nm, the AAO layer32 can have pores 33 (FIG. 4B) having diameters of approximately 200 nmand separated by distances on the order of 250 nm, and the AAO layer 38can have pores having diameters of approximately 50 nm and separated bydistances slightly larger than 50 nm.

In addition to using an AAO layer as a light guiding and/or diffusivelayer in a light guiding structure as described herein, an AAO layeralso can be used as a mask layer. For example, an AAO layer can be usedto facilitate engineering a fluoropolymer layer having a targetpatterned surface (e.g., a nano-patterning). To this extent, FIGS. 6A-6Cshow an illustrative process for patterning a fluoropolymer layer 26according to an embodiment. As shown in FIG. 6A, a structure includingan AAO layer 18 having exposed pores 19 can be obtained (e.g.,fabricated) using any solution. As shown in FIG. 6B, a fluoropolymerlayer 26 can be formed directly on the AAO layer 18 and allowed to flow(e.g., by heating) such that the fluoropolymer penetrates the pores 19in the AAO layer 18. As shown in FIG. 6C, the AAO layer 18 and thefluoropolymer layer 26 can be detached using any solution, such asmechanical lift-off, AAO etching, and/or the like, which will result inthe fluoropolymer layer 26 having the patterned surface 42.

The surface patterning 42, such as a nano-scale surface patterning, canbe configured to result in formation of a photonic crystal within thefluoropolymer layer 26, which can provide effective reflection and/orwave guiding of light. To this extent, FIGS. 7A and 7B show illustrativeutilizations of surface-patterned fluoropolymer layers in a lightguiding structure according to embodiments. In FIG. 7A, light emittedfrom a light source 20 can propagate along a light guiding region 46 ofa fluoropolymer layer 44. The light guiding region 46 is surrounded by aphotonic crystal formed by nano-scale pillars 48 formed on the surfaceof the fluoropolymer layer 44 as described herein. In FIG. 7B, thefluoropolymer layer 26 including a patterned surface 42 as shown in FIG.6C is used to provide diffused scattering of light emitted byoptoelectronic devices 20A, 20B, located on an opposing surface of thefluoropolymer layer 26 as the patterned surface 42.

While shown and described in conjunction with fluoropolymer materials,it is understood that a similar process can be utilized with othermaterials, such as fused silica, and/or the like. In another embodiment,a glass layer including an array of holes can be deposited over afluoropolymer layer located on the AAO layer. A second fluoropolymerlayer can be deposited over the glass layer and allowed to flow so thatthe fluoropolymer penetrates the holes in the glass layer. Subsequently,the glass layer can be removed, e.g., by etching.

FIGS. 8A-8F show an illustrative process for forming a light guidingstructure according to an embodiment. As shown in FIG. 8A, an AAO layer18 can be obtained using any solution, e.g., fabricated as describedherein. In FIG. 8B, a handler layer 50 can be applied to a top surfaceof the AAO layer 18 using any solution. For example, as describedherein, the handler layer 50 can be formed of a fluoropolymer, which isallowed to flow sufficiently to enable the AAO layer 18 to be securedthereto. In an embodiment, the handler layer 50 is formed of atransparent material (e.g., ultraviolet transparent material), such asthe fluoropolymer, and is utilized within a resulting light guidingstructure. Alternatively, the handler layer 50 can be removed, and notincluded in the light guiding structure.

In FIG. 8C, the substrate 14 and aluminum layer 16 shown in FIG. 8A areremoved from the opposing surface of the AAO layer 18 using anysolution. For example, the substrate 14 and aluminum layer 16 can beremoved using a voltage pulse process described herein. In FIG. 8D, alayer of filler material 52A, 52B can be applied (e.g., deposited,placed, and/or the like) to the top and/or bottom surfaces of thestructure shown in FIG. 8C. For example, the filler material 52A can beapplied on the handler layer 50, while the filler material 52B can beapplied to the opposing surface of the AAO layer 18. Additionally, theentire structure can be encapsulated with a fluoropolymer encapsulant 54using any solution. The filler material 52B can comprise any materialthat can be removed (e.g., etched) from the fluoropolymer encapsulant 54using a process that does not damage the fluoropolymer encapsulant 54,such as, for example, silicon dioxide.

In FIG. 8E, openings 56A, 56B are formed in the fluoropolymerencapsulant 54 to expose the filler material 52A, 52B to the ambient.The openings 56A, 56B can be formed using any solution, such asmechanical removal of the fluoropolymer encapsulant using a drill,puncture, and/or the like, localized heating and/or chemical removal,etc. While the openings 56A, 56B are shown located on a side of thestructure, it is understood that an opening 56A, 56B can be located inany desired location. Furthermore, it is understood that an opening 56A,56B can have any dimension. While a single opening 56A, 56B for eachlayer of filler material 52A, 52B is shown and described herein, it isunderstood that embodiments can use more than one opening 56A, 56B for alayer of filler material 52A, 52B.

As shown in FIG. 8F, the filler material 52A, 52B (FIG. 8D) can beremoved from the fluoropolymer encapsulant 54 using any solution. Forexample, the filler material 52A, 52B can be removed using a chemicaletching approach. In this case, the structure can be placed in a bath ofa chemical that reacts with (e.g., dissolves) the filler material 52A,52B, but preserves the fluoropolymer encapsulant 54. The chemical canpass through the openings 56A, 56B (FIG. 8E) and react with and etch thefiller material 52A, 52B. For example, when the filler material 52A, 52Bis silicon dioxide, the chemical can be hydro-fluoric acid. However, itis understood that this is only illustrative of various chemicals andfiller material 52A, 52B that can be utilized. However, it is understoodthat any material that can be readily applied and dissolved, such assilicon nitride, and/or the like, can be utilized as the filler material52A, 52B.

Subsequently, the openings 56A, 56B (FIG. 8E) can be sealed using anysolution. In an embodiment, the openings 56A, 56B are sealed using asealing material 58A, 58B. The sealing material 58A, 58B can be anymaterial that can effectively bind to the fluoropolymer encapsulant 54and is sufficiently stable over a target time period, such as a suitabletype of epoxy. In an embodiment, the sealing material 58A, 58B is afluoropolymer-based material, which is placed over the opening andheated to bind with the fluoropolymer encapsulant 54. However, it isunderstood that this is only illustrative, and other approaches, such asthe use of a mechanical sealant, and/or the like, can be utilized. Asillustrated, the process results in two layers 60A, 60B filled with afluid, such as ambient air. In an embodiment, the process can furtherinclude filling one or more of the layers with a liquid, such aspurified water as defined by the U.S. Food and Drug Administration,prior to sealing the corresponding opening 58A, 58B.

Embodiments further provide for the inclusion of one or more opticalelements in the light guiding structure. As used herein, an opticalelement is a structure configured to extract, emit, sense, redirect,scatter, diffuse, focus, and/or the like, radiation propagating withinor outside the light guiding structure. For example, one or more regionsof a surface of a fluoropolymer layer described herein can includeroughness elements for providing a diffusive output surface, which canbe created using standard imprinting technology. Additionally, one ormore lenses (e.g., Fresnel lenses), and/or the like, can be included ona surface of a fluoropolymer layer described herein. To this extent, alens, such as a Fresnel lens, can be imprinted onto the surface, a lenscan be deposited over and embedded into the surface (e.g., by flowingthe fluoropolymer), and/or the like. Such a lens can be fabricated fromany transparent material including sapphire, fused silica, afluoropolymer, and/or the like.

While shown and described herein as a method of fabricating a structureincluding a light guiding structure, it is understood that aspects ofthe invention further provide various alternative embodiments. Forexample, embodiments of the invention further include the variousstructures shown and described herein. Additionally, embodiments of theinvention include systems, such as ultraviolet-based sterilizationsystems, which incorporate a structure described herein, as well as thefabrication of such systems. To this extent, the fabrication of such asystem can include integrating a structure described herein as well asconnecting one or more of the electronic devices described herein to acontrol system capable of providing power to and operating theelectronic device in a desired manner. Such integration and connectionscan be performed using any solution.

The foregoing description of various aspects of the invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed, and obviously, many modifications and variations arepossible. Such modifications and variations that may be apparent to anindividual in the art are included within the scope of the invention asdefined by the accompanying claims.

What is claimed is:
 1. A structure including: a first anodized aluminumoxide (AAO) layer; a second AAO layer located on the first AAO layer;and an optoelectronic device coupled to a side of at least one of: thefirst AAO layer or the second AAO layer, wherein the optoelectronicdevice is positioned at a target angle with respect to light propagatingthrough the at least one of: the first AAO layer or the second AAOlayer, wherein the first and second AAO layers have distinct opticalproperties.
 2. The structure of claim 1, further comprising a couplercoupling the optoelectronic device to the side of the at least one of:the first AAO layer or the second AAO layer, wherein the coupler isformed of a transparent material.
 3. The structure of claim 2, whereinthe coupler is formed of a fluoropolymer.
 4. The structure of claim 1,wherein the optoelectronic device is coupled to an edge of the at leastone of: the first AAO layer or the second AAO layer.
 5. The structure ofclaim 1, wherein the optoelectronic device is an ultraviolet lightemitting device and the target angle provides maximum light guiding ofthe ultraviolet light emitted by the ultraviolet light emitting device.6. The structure of claim 1, further comprising a fluoropolymer layerlocated between the first AAO layer and the second AAO layer.
 7. Thestructure of claim 1, further comprising: a fluoropolymer layer locatedadjacent to one of: the first AAO layer or the second AAO layer; and areflective layer located adjacent to a surface of the fluoropolymerlayer opposite the one of: the first AAO layer or the second AAO layer.8. The structure of claim 7, further comprising a gap layer locatedbetween the reflective layer and the fluoropolymer layer, wherein thegap layer comprises a transparent fluid.
 9. The structure of claim 1,wherein the first and second AAO layers provide a graded index ofrefraction.
 10. A light guiding structure comprising: a plurality ofanodized aluminum oxide (AAO) layers; and a plurality of fluoropolymerlayers alternating with the plurality of AAO layers, wherein lightpropagates through the light guiding structure in a directionsubstantially parallel to the layers, and wherein the plurality of AAOlayers have a plurality of distinct optical properties.
 11. Thestructure of claim 10, further comprising a reflective layer locatedadjacent to a surface of at least one of the plurality of fluoropolymerlayers.
 12. The structure of claim 11, further comprising a gap layerlocated between the reflective layer and the at least one of theplurality of fluoropolymer layers, wherein the gap layer comprises atransparent fluid.
 13. The structure of claim 10, wherein the pluralityof AAO layers provide a graded index of refraction.
 14. The structure ofclaim 10, further comprising: an optoelectronic device coupled to anedge of the light guiding structure, wherein the optoelectronic deviceis positioned at a target angle with respect to the light propagatingthrough the light guiding structure; and a coupler coupling theoptoelectronic device to the side of the light guiding structure,wherein the coupler is formed of a transparent material.
 15. A methodcomprising: fabricating a structure including: a first anodized aluminumoxide (AAO) layer; and a fluoropolymer layer located immediatelyadjacent to a surface of the first AAO layer, wherein light propagatesthrough the first AAO layer in a direction substantially parallel to thefluoropolymer layer; and patterning a surface of the fluoropolymer layeropposite the first AAO layer using a second AAO layer.
 16. The method ofclaim 15, further comprising coupling an optoelectronic device to a sideof the first AAO layer using a transparent material, wherein theoptoelectronic device is positioned at a target angle with respect tothe light propagating through the first AAO layer.
 17. The method ofclaim 15, further comprising applying a reflective layer over a surfaceof the fluoropolymer layer opposite the first AAO layer.
 18. The methodof claim 15, further comprising fabricating a gap layer immediatelyadjacent to a surface of the fluoropolymer layer opposite the first AAOlayer.
 19. The method of claim 15, further comprising forming a thirdAAO layer immediately adjacent to a surface of the fluoropolymer layeropposite the first AAO layer.
 20. The method of claim 15, wherein thepatterning forms a photonic crystal in the fluoropolymer layer.